Dwarf Honey Gourami Illness Help!

[jojo45]

Need some help for the past couple of days one of my dwarf honey gourami has been turning black and seems really rigid (not using tail fin to swim) also constantly at the surface, appetite is still good and still interacting with the other fish but now the other two have started to go black here's some pics

 

[KISSfn]

Is your filter cycled? What are your Ammonia and Nitrite readings in mg/l?

 

[Essjay]

Can I ask a silly question, what colour are the gouramis, and where on their bodies are they going black? The males of the wild coloured form have black throats when they are mature. Stressed males (or newly bought males) will not have this black, it will appear once they are no longer stressed, or when new ones have settled in.